Bob Lutz: Greinke vs. Arrieta – who do you have?

Since he walked six and gave up three hits and four earned runs in a start against Cleveland on June 16 – eons ago – Jake Arrieta has become invincible.

And that’s only a slight exaggeration.

The 29-year-old Arrieta, who pitches for the Chicago Cubs, has been ridiculously good all season. When three runs and six walks in five innings is your low point, chances are things are going well.

In 18 starts since that performance against the Indians, Arrieta has pitched 134 innings and allowed only 73 hits and 14 earned runs. That’s right, 14 earned runs in more than three months. His ERA during that span, which includes a no-hitter against the Los Angeles Dodgers, is 0.94.

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When Arrieta gives up a run, it comes across the ticker at the bottom of your television screen. Children get out of school early.

Yet even with Arrieta’s crazy overall numbers – he’s 20-6 with a 1.88 ERA and is as responsible as anyone for the Cubs’ National League rise – it’s a long shot that he’ll win the National League Cy Young Award.

The frontrunner, the leader from the start of the season until now, is the Dodgers’ Zack Greinke, who had only six wins through the season’s first three months because LA did not give him any run support.

But the Dodgers have been scoring for Grienke lately and he’s all the way up to 18 wins – with only three losses – and has a miniscule 1.65 ERA, the lowest since Greg Maddux (1.63) in 1995.

In fact, Grienke has the seventh lowest ERA since 1943, when the Yankees’ Spud Chandler had a 1.64 ERA. Maddux (1.54, 1994), Dwight Gooden (1.53, 1985), Luis Tiant (1.60, 1968), Maddux (1.63, 1995) and Bob Gibson (1.12, 1968) are the only pitchers with a lower ERAs than Greinke over the past 72 years.

Incidentally, 40 of the 41 lowest ERAs in MLB history – all except for Gibson’s all-time best – came before 1920.

Greinke could easily be 25-2 or something crazy like that. Same for Arrieta. Both are having seminal seasons and for Arrieta, it’s come a little from left field.

He’s been a good pitcher for the Cubs for a while now, but had never won more than 10 games in any season before 2015.

He was just 4-4 through May with an ERA of 3.18. Since the start of June, Arrieta is 16-2 with a 1.31 ERA. And he’s 9-0 since the beginning of August with an 0.48. You need the Hubble Space Telescope to find this guy’s ERA.

Greinke, meanwhile, had just an awful month in August, when he was 4-1 with a 2.45 ERA. “Awful” being relative, of course.

He’s actually been incredibly consistent with montly ERAs of 1.95, 1.05, 1.74, 0.95, 2.45 and 1.91. He was 8-2 with a 1.39 ERA before the All-Star break and 10-1 with a 2.03 ERA since. He’s 9-1, 1.48 at home; 9-2, 1.83 on the road. And he’s going to opt out of his contract after this season and sign with somebody for a gazillion dollars.

Arrieta has been consistent, too, but there is some difference in his numbers at home in Wrigley Field and on the road. He’s been only marvelous at home with an 8-5 record and 2.11 ERA. On the road, he’s been other-worldly, going 12-1 with a 1.68 ERA.

It looks like Greinke and Arrieta will become the first two pitchers in either league with sub-2.00 ERAs since the New York Mets’ Gooden (1.53) and St. Louis’ John Tudor (1.93) accomplished the feat in the National League 30 years ago.

Greinke was scheduled to make three more starts before the end of the regular season, starting with tonight against Arizona. But he’s been scratched from that start because of a sore calf muscle. He is attempting to win 20 games in a season for the first time in his career and has two scheduled starts remaining, although the Dodgers are almost certainly headed to the NL playoffs and could decide to give him some rest.

Arrieta, meanwhile, has two remaining starts, including a big one Sunday against the Pittsburgh Pirates. He’s scheduled to make his final regular-season start on Oct. 2 at Milwaukee.

Give Arrieta credit for bringing a debate to the National League Cy Young discussion. In almost any other season Greinke’s numbers would have blown away the field. Not this time, though.

I still favor Greinke, but want to see what happens down the stretch – especially Arrieta’s start against the Pirates – before making it official.